Front or rear drive conversion

[x332race]

I am new to ebikes but am considering converting my old Cannondale M800. This has aluminum front forks and I have heard that problems can occur fitting motor to aluminum front forks although I have seen conversions in other threads which seem to have been fitted to aluminum forks.

Should I go for front or rear wheel drive? Front seems to be easier to fit and better weight distribution....

I will only be using the bike for road use.

 

[JuicyBike]

You've got it - for ease and weight distribution (fewer wheelies) use the front, however, the strain on the forks increases. So, you might consider better forks and headset, or just wait and see. Distance between the drop-outs is usually the limiting factor. For most FW kits this is around 100mm.

 

[x332race]

The forks are good quality. What usually fails on aluminum forks? Distance between dropouts is 100mm. Don't really want to go down route of new forks etc.

 

[kitchenman]

I think the forks on my Cannondale CX700 are Ali .. I'll check when I get home as I cant find anything online which is a bit disappointing! .. I used my CX700 with a front hub motor for just over a year. My motor was a Tongxin 180 watt 175 rpm. For me this provided enough assistance to get me comfortably to work and back. 15 miles each way with 3 significant hills! ..

 

[JuicyBike]

If you're near our shop in Buxton, you'd be welcome to come and have a closer look at our kits.

 

[kitchenman]

The forks are good quality. What usually fails on aluminum forks? Distance between dropouts is 100mm. Don't really want to go down route of new forks etc.

mine are 100mm.

 

[catsnapper]

Although most forks have the required 100mm dropout width for the front hub axle, they don't all have the clearance for the larger hub size. It's not uncommon for the taper of the fork blades or the dropouts not being on the inside of the blades, to cause the hub to rub or be impossible to fit.
Take care that your existing forks or any replacement ones have the required clearance.

I have one set of forks that will not take a 250W Bafang hub, but will accept a larger diameter 400W Ezee hub because of the different hub design. Both are 100mm OLD.

Alan

 

[x332race]

Although most forks have the required 100mm dropout width for the front hub axle, they don't all have the clearance for the larger hub size. It's not uncommon for the taper of the fork blades or the dropouts not being on the inside of the blades, to cause the hub to rub or be impossible to fit.
Take care that your existing forks or any replacement ones have the required clearance.

I have one set of forks that will not take a 250W Bafang hub, but will accept a larger diameter 400W Ezee hub because of the different hub design. Both are 100mm OLD.

Alan

Just checked....the forks on the Cannondale are 100mm dropout width but clearance higher up is only 80mm so that might be a problem. I do have another bike with front shocks (again aluminum) that have 100mm clearance all the way up, so I may have to use that bike instead if I go down the route of a front motor. Should I fit a torque arm?

 

[JuicyBike]

In general, if you have 100mm width, for 80mm along the blades from the drop-outs, you should be fine, for most kits... Ours are 98mm for 50mm. Very wise to check.

 

[bode]

You've got it - for ease and weight distribution (fewer wheelies) use the front,

But you can get wheelspin from a front hub, especially when starting off on gravelly surfaces, while you generally get better traction from a rear hub because more of the weight is there. Though of course a front hub is easier to fit.

 

[rustic]

Yep, I'm considering a front hub conversion at the moment. I had this set up on my Alien GSII and was quite happy with it. From memory the only difficulty I ever had with wheelspin was on the ice one day, but riding conditions would have been tough on any bike that day.

Jim at Alien highlighted a problem with converting my current Giant Cypress bike - I currently have combined brake / gear change levers, so would need to buy seperate gear change levers once the motor cut out brakes have been fitted. This would also increase the demand on the handlebar space which is already a bit tight.

 

[Deleted member 4366]

Life's full of choices and every one has advantages and disadvantages. There's no answer to which is best on your bike. First question to answer is what motor you want to use.

You normally have to open up (file) the drop-outs a little to take a 250w hub motor and a lot if you want a more powerful one. Your forks look a bit spindly, so, if they'e ally alloy, they might not be strong enough without some means of reinforcement. If you go for a rear motor, you'll lose your cassette and possibly one gear, which is not such a problem because you probably won't need first gear anymore. However, most free-wheel sets only go down to 14T, so you end up needing a bigger chainwheel to pedal past 15mph.. If it were me doing it. I'd buy a pair of used medium quality suspension forks from Ebay and fit them, and keep your forks in case you want to convert back. It's only a 10 minute job to change forks, so it's only a quaestion of cost and you won't mind filing the drop-outs in these forks or bolting on torque arms or whatever. Plus, it'll give you a chance to upgrade to a nice hydraulic disc brake, which will be an advantage with the additional weight of the electrical stuff.

 

[bode]

Jim at Alien highlighted a problem with converting my current Giant Cypress bike - I currently have combined brake / gear change levers, so would need to buy seperate gear change levers once the motor cut out brakes have been fitted. This would also increase the demand on the handlebar space which is already a bit tight.

Assuming that your combined gear/brake setup only applies to one lever, you could just have a motor cutout on the other lever; also assuming that you always use both brakes more or less simultaneously.

 

[x332race]

Yep, I'm considering a front hub conversion at the moment. I had this set up on my Alien GSII and was quite happy with it. From memory the only difficulty I ever had with wheelspin was on the ice one day, but riding conditions would have been tough on any bike that day.

Jim at Alien highlighted a problem with converting my current Giant Cypress bike - I currently have combined brake / gear change levers, so would need to buy seperate gear change levers once the motor cut out brakes have been fitted. This would also increase the demand on the handlebar space which is already a bit tight.

I have this problem too, I realise!

 

[Deleted member 4366]

Jim at Alien highlighted a problem with converting my current Giant Cypress bike - I currently have combined brake / gear change levers, so would need to buy seperate gear change levers once the motor cut out brakes have been fitted. This would also increase the demand on the handlebar space which is already a bit tight.

Don't change your brake levers. Instead buy a couple of the cheapest cycle computers on Ebay - about £2 each. That's if you want two brake switches, otherwise just get one for the back brake.
Cut the sensor (the bit that clips to your forks) off the end, but leave a bit of wire on it .
Cut the connector off the kit brake levers leaving an appropriate length of wire.
Join the two pairs of wires together.
For the back brake, screw the magnet to the exposed cable where it runs along the cross-bar, and fix the sensor to the frame with the cable ties - like it's supposed to be fixed to the forks. Adjust the positions so that when the brake is pulled, the magnet moves towards the sensor and switches it off in the right position.
For the front brake, you need to fit the magnet to wherever you can on the cable or calliper that moves where you can fix the sensor nearby to get the right switching effect. Not quite as easy as the back one, but easier to do than describe, once you see the back one working.

 

[rustic]

Assuming that your combined gear/brake setup only applies to one lever, you could just have a motor cutout on the other lever; also assuming that you always use both brakes more or less simultaneously.

Yeah, sadly, both levers are combined brake / gear levers.

 

[rustic]

Don't change your brake levers. Instead buy a couple of the cheapest cycle computers on Ebay - about £2 each. That's if you want two brake switches, otherwise just get one for the back brake.
Cut the sensor (the bit that clips to your forks) off the end, but leave a bit of wire on it .
Cut the connector off the kit brake levers leaving an appropriate length of wire.
Join the two pairs of wires together.
For the back brake, screw the magnet to the exposed cable where it runs along the cross-bar, and fix the sensor to the frame with the cable ties - like it's supposed to be fixed to the forks. Adjust the positions so that when the brake is pulled, the magnet moves towards the sensor and switches it off in the right position.
For the front brake, you need to fit the magnet to wherever you can on the cable or calliper that moves where you can fix the sensor nearby to get the right switching effect. Not quite as easy as the back one, but easier to do than describe, once you see the back one working.

Ta for the suggestion, I think I'd probably opt for new gear changers to be honest D8veh, I do have an idea for a way round all this to solve all the issues I have with electric bikes / kits, but will only post if successful!

 

[x332race]

Don't change your brake levers. Instead buy a couple of the cheapest cycle computers on Ebay - about £2 each. That's if you want two brake switches, otherwise just get one for the back brake.
Cut the sensor (the bit that clips to your forks) off the end, but leave a bit of wire on it .
Cut the connector off the kit brake levers leaving an appropriate length of wire.
Join the two pairs of wires together.
For the back brake, screw the magnet to the exposed cable where it runs along the cross-bar, and fix the sensor to the frame with the cable ties - like it's supposed to be fixed to the forks. Adjust the positions so that when the brake is pulled, the magnet moves towards the sensor and switches it off in the right position.
For the front brake, you need to fit the magnet to wherever you can on the cable or calliper that moves where you can fix the sensor nearby to get the right switching effect. Not quite as easy as the back one, but easier to do than describe, once you see the back one working.

Great idea.....think that should work for me...thanks!

 

[TwoBikes]

Regarding brake cut-outs: You don't say what you're going to use as a throttle, but if it's a twist grip with a return spring (rather than, say, a push button), and you don't have cruise control, you could do without the brake cut-out switches completely. One of my electric bikes has them, the other doesn't, and I haven't got into any scrapes with the one that doesn't. Same for our trikes - one has them and the other doesn't.

Regarding motor width: You can get drawings of the motors that BMSBattery sell, on their website. These give the clearances for various parts of the motor housing. I used these to choose a motor for a bike with 89mm front fork dropout width - and it clears the forks, but by only about 2mm! You could deliberately order a slim motor (for example the Cute Q85): it comes with thick anti-spin spacers that can be used either on the outside of narrow forks or on the inside of wide forks.

 

[Deleted member 4366]

Regarding brake cut-outs: You don't say what you're going to use as a throttle, but if it's a twist grip with a return spring (rather than, say, a push button), and you don't have cruise control, you could do without the brake cut-out switches completely. One of my electric bikes has them, the other doesn't, and I haven't got into any scrapes with the one that doesn't.

There is a risk of not having brake switches. I was going up a hill on a non-suspension bike and I hit a bump (probably pothole) at full throttle. The bump jerked my arm which broke the rather weak plastic throttle and one of the magnets fell out, which left it permanently on 2/3 throttle. Luckily, I had brake switches, which I was able to use to control it so that I could drive my bike home. Also, water in the throttle can leave it permanently on. As it's so simple, cheap and non-intrusive to put a switch on a back cable-operated brake using the method I mentioned above, it's a no-brainer to do it as a minimum.